Anticataleptic potencies of glutamate-antagonists.

The anticataleptic effects of non-competitive and competitive NMDA antagonists as well as those of an agonist at the allosteric glycine binding site of the NMDA receptor were tested in the catalepsy model. Some of these drugs were further tested in a reaction time task demanding rapid locomotor initiation. The results show that the non-competitive NMDA antagonists dizocilpine and memantine as well as the competitive antagonists CGP 39551, CGP 37849 and CPPene antagonized dopamine D2 receptor mediated catalepsy induced by haloperidol. D-cycloserine, a partial glycine agonist per se had no effects, but it enhanced the anticataleptic effects of dizocilpine when coadministered. However, the effects of CGP 37849 were abolished. Dopamine D1 receptor mediated catalepsy induced by SCH 23390 was antagonized by dizocilpine, memantine, CPPene, but not by CGP 37849. In the reaction time task dizocilpine, memantine and CGP 37849 were tested for their anti-akinetic and anti-bradykinetic potencies. All these compounds improved haloperidolinduced slowing of reaction time. However, they acted differentially on haloperidol-induced slowing of movement execution and decreased initial acceleration. Thus, antagonists at the NMDA receptor may have a therapeutic potential in the treatment of Parkinson's disease. Their potency can be manipulated specifically at the glycine binding site.